systemd-system.conf(5) System and session service manager configuration file

Other Alias






When run as system instance systemd reads the configuration file system.conf, otherwise user.conf. These configuration files contain a few settings controlling basic manager operations.


All options are configured in the [Manager] section:

LogLevel=, LogTarget=, LogColor=, LogLocation=, DumpCore=yes, CrashShell=no, ShowStatus=yes, CrashChVT=1, DefaultStandardOutput=journal, DefaultStandardError=inherit

Configures various parameters of basic manager operation. These options may be overridden by the respective command line arguments. See systemd(1) for details about these command line arguments.


Configures the initial CPU affinity for the init process. Takes a space-separated list of CPU indexes.


Configures in which control group hierarchies to create per-service cgroups automatically, in addition to the name=systemd named hierarchy. Defaults to cpu. Takes a space separated list of controller names. Pass the empty string to ensure that systemd does not touch any hierarchies but its own.

Note that the default value of 'cpu' will make realtime scheduling unavailable to system services. See m[blue]My Service Can't Get Realtime!m[][1] for more information.

JoinControllers=cpu,cpuacct,cpuset net_cls,netprio

Configures controllers that shall be mounted in a single hierarchy. By default systemd will mount all controllers which are enabled in the kernel in individual hierarchies, with the exception of those listed in this setting. Takes a space separated list of comma separated controller names, in order to allow multiple joined hierarchies. Defaults to 'cpu,cpuacct'. Pass an empty string to ensure that systemd mounts all controllers in separate hierarchies.

Note that this option is only applied once, at very early boot. If you use an initial RAM disk (initrd) that uses systemd it might hence be necessary to rebuild the initrd if this option is changed, and make sure the new configuration file is included in it. Otherwise the initrd might mount the controller hierarchies in a different configuration than intended, and the main system cannot remount them anymore.

RuntimeWatchdogSec=, ShutdownWatchdogSec=

Configure the hardware watchdog at runtime and at reboot. Takes a timeout value in seconds (or in other time units if suffixed with ms, min, h, d, w). If RuntimeWatchdogSec= is set to a non-zero value the watchdog hardware (/dev/watchdog) will be programmed to automatically reboot the system if it is not contacted within the specified timeout interval. The system manager will ensure to contact it at least once in half the specified timeout interval. This feature requires a hardware watchdog device to be present, as it is commonly the case in embedded and server systems. Not all hardware watchdogs allow configuration of the reboot timeout, in which case the closest available timeout is picked. ShutdownWatchdogSec= may be used to configure the hardware watchdog when the system is asked to reboot. It works as a safety net to ensure that the reboot takes place even if a clean reboot attempt times out. By default RuntimeWatchdogSec= defaults to 0 (off), and ShutdownWatchdogSec= to 10min. These settings have no effect if a hardware watchdog is not available.


Controls which capabilities to include in the capability bounding set for PID 1 and its children. See capabilities(7) for details. Takes a whitespace separated list of capability names as read by cap_from_name(3). Capabilities listed will be included in the bounding set, all others are removed. If the list of capabilities is prefixed with ~ all but the listed capabilities will be included, the effect of the assignment inverted. Note that this option also affects the respective capabilities in the effective, permitted and inheritable capability sets. The capability bounding set may also be individually configured for units using the CapabilityBoundingSet= directive for units, but note that capabilities dropped for PID 1 cannot be regained in individual units, they are lost for good.


Sets the timer slack in nanoseconds for PID 1 which is then inherited to all executed processes, unless overridden individually, for example with the TimerSlackNSec= setting in service units (for details see systemd.exec(5)). The timer slack controls the accuracy of wake-ups triggered by timers. See prctl(2) for more information. Note that in contrast to most other time span definitions this parameter takes an integer value in nano-seconds if no unit is specified. The usual time units are understood too.

DefaultLimitCPU=, DefaultLimitFSIZE=, DefaultLimitDATA=, DefaultLimitSTACK=, DefaultLimitCORE=, DefaultLimitRSS=, DefaultLimitNOFILE=, DefaultLimitAS=, DefaultLimitNPROC=, DefaultLimitMEMLOCK=, DefaultLimitLOCKS=, DefaultLimitSIGPENDING=, DefaultLimitMSGQUEUE=, DefaultLimitNICE=, DefaultLimitRTPRIO=, DefaultLimitRTTIME=

These settings control various default resource limits for units. See setrlimit(2) for details. Use the string infinity to configure no limit on a specific resource. These settings may be overridden in individual units using the corresponding LimitXXX= directives. Note that these resource limits are only defaults for units, they are not applied to PID 1 itself.